The invention concerns an apparatus for mounting a flipchip on a work piece.
For mounting onto a work piece, for example a BGA(copyright) substrate or a printed circuit board, semiconductor chips are normally presented so that their active surface is facing upwards. However, certain semiconductor chips, in particular microprocessors, have to be turned (flipped) before mounting on the work piece so that their active surface faces towards the work piece. For this reason, such semiconductor chips are generally called flipchips. In order that the structures of the flipchip match the structures of the work piece, the position and orientation of the structures of the flipchip as well as the structures of the work piece have to be determined before placing the flipchip onto the work piece.
Under the name of Micron, the applicant markets an apparatus for mounting flipchips with which the flipchip is first flipped, then picked up by a pick-up tool and transported to a stationary position acquisitioning device where it is measured and then finally transported to the work piece and placed. A conventional CCD camera with, for example, 480xc3x97640 pixels serves as the position acquisitioning device. The stationary arrangement of the position acquisitioning device results in a time loss as each flipchip must first be transported to the position acquisitioning device and only after this can it be transported to the work piece.
In order to avoid this time loss, in Patent Specification U.S. Pat. No. 5,768,759 it has been suggested to arrange a stationary mirror close to the work piece and a camera next to the pickup tool so that, on crossing the mirror, the active surface of the picked up flipchip is located in the field of vision of the camera. Up till now, technological difficulties have prevented the practical realisation of this solution.
The object of the invention is to accelerate the acquisition of the position and orientation of the flipchip during mounting and thereby increase the capacity of the automatic assembly machine.
An apparatus for mounting a flipchip onto a work piece comprises at least one pick-up station where the flipchips are presented, a transport mechanism movable in horizontal x and y directions with a pick-up tool for pick-up and transport of the flipchip from the pick-up station to, the work piece, and a position acquisitioning device arranged on the transport mechanism for determining the position and orientation of the picked up flipchip. In accordance with the invention, a single line camera is foreseen as the position acquisitioning device which, during the transport of the flipchip from the pick-up station to the work piece, is moved across under the flipchip where it scans an image of the surface of the flipchip and transmits it to an image processing module. For this purpose, a linear guide element for guiding a slide movable in a predetermined direction, a drive mechanism for driving the slide and a measuring device for determining the position of the slide are foreseen on the transport mechanism. The single line camera is secured to the slide and its field of vision is directed upwards towards the active surface of the flipchip.
In the following, embodiments of the invention are explained in more detail based on the drawing.